The granny-low 4 speed has the lowest 1st gear ratio of any single range transmission. Ever. 7.20:1 if I'm not mistaken. Tied to any rear end you're going to have a crawler. My 49 has one and a 4.56:1 rear. At full wind out (2800rpm) it's doing about 8-10mph. The 4speed box will take plenty of torque. I think it is an SM420, but I'm terrible with names.
Find a 1 ton dually rear and it may have a 5.14 gearset. Great for pushing, but you might take 3 days to go from your house to your local track...
Current fleet (subject to change w/o notice) \'49 GMC 3/4-Ton , 60 Austin Healey Frog-eye Sprite (some assembly required), 2011 Dodge Avenger, 2015 Jeep Cherokee. No, they don't all run. My other ride is a (B737)no, (B767)no, A320.... Update... was Embraer E190, now Boeing B787. Knowledge is a wonderful thing, but ignorance means you don't know you can't do something.
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